It is well known that mercury is a toxic and/or ecotoxic compound in all of its organic forms and in respect of all of its chemical states.
The reason is that mercury accumulates within organisms and is the cause of numerous diseases, affecting particularly the kidneys, the digestive system, and the neurological system.
Of all the oxidation states, it is the ions of mercury II, Hg2+, that are the most toxic.
The development of selective sensors for this element is of particular interest for the purposes of quantifying and detecting this element in the natural environment, water, and foods.
Moreover, determining the concentration of mercury in water intended for food use is necessary within the context of regulations concerning drinking water and concerning hazardous materials.
The technique used at present for quantifying mercury in water is that of atomic absorption spectroscopy.
This technique, although accurate and reliable, has a number of drawbacks.
In particular, it involves heavy equipment which is difficult to transport.
Mercuric compounds may also be detected using selective fluorescent and colorimetric sensors, by grafting chromophores or fluorophores onto dithia-dioxa-monoaza crown ether compounds.
The dithia-dioxa-monoaza crown ether compounds complex the Hg2+ ions selectively, and this complexation produces a change in the properties of the chromophores or fluorophores bound to them.
This change in optical properties of the chromophores or of the fluorophores is due to an electron-attracting effect of the mercury, which depletes the chromophore.
Accordingly, Zhu et al. in Org. Lett., 2008, 10, 1481-1484, propose a chemical sensor for mercuric ions Hg2+, in which a dithia-dioxa-monoaza crown ether compound, to which a tricarbocyanine dye is grafted, is used to complex the Hg2+ ions, and thus causes a change in color of the dye when the Hg2+ ions are complexed by the crown ether.
This change in color is visible to the naked eye.
However, this technique does not allow the detection of small quantities of Hg2+ ions and, moreover, does not allow the concentration of Hg2+ in the sample under analysis to be determined.
The same document indicates that the detection of mercuric ions Hg2+ may also be accomplished by analyzing the fluorescence emitted by the dye grafted onto the crown ether.
This technique, apart from the impossibility of determining the concentration of Hg2+ ions, has the drawback of having to be performed under reduced-light conditions, and this does not allow it to be performed directly on site.
U.S. Pat. No. 7,385,267 B2 describes electrical devices in which nanotubes or nanowires of a conductor material are functionalized with a molecule which undergoes a change in property on contact with an analyte for detecting within a sample.
This device allows the analyte in the sample to be detected by detecting the change in property of the conductor material.
There is no reference in that document to the detection of Hg2+ ions or to the modification of the conduction properties of a semiconductor material grafted with a compound which complexes mercuric ions Hg2+ when contacted with the Hg2+ ions.
Accordingly, a need exists for an apparatus for detecting and/or quantifying Hg2+ ions that are present in gaseous form or in solution in water or in an unknown solvent, it being possible for said apparatus to be used on site, irrespective of the light conditions, and to be transportable.